Occlusal Plane Stability After Curvilinear Mandibular Distraction Osteogenesis

Curvilinear mandibular distraction osteogenesis (MDO) allows for mandibular lengthening in both the sagittal and vertical planes. However, the stability of these results is less well known. This study examines the stability of the occlusal plane changes in patients who have undergone curvilinear MDO in mixed dentition, with and without orthodontics. We performed a retrospective review of patients who underwent curvilinear MDO at our institution from 2009 to 2024. Cephalometric analysis was conducted on preoperative, immediate, and extended postoperative lateral cephalograms, lateral radiographs, or CT scans considering Sella-nasion-B point angle (SNB), SN-mandibular plane angle (MPA), and SN-occlusal plane angle (OPA). Twenty-five patients underwent curvilinear MDO in mixed dentition and had requisite pre-op and immediate post-op photographs, of which 15 had extended postoperative imaging. Average age at surgery was 8±5 years, with an average follow-up of 4±3 years. Thirty-two percent (n=8) of patients were tracheostomy-dependent preoperatively, with 50.0% (n=4) decannulated postoperatively. Average distraction distance was 30±8 millimeters. Fifty-six percent (n=14) underwent postoperative orthodontic treatment. Pre-op SNB was 69±6 degrees improving to 76±7-degree post-op (P<0.001) and maintained at 73±7 degrees (P<0.001). Pre-op MPA was 57±12 degrees changing to 48±11-degree post-op (P<0.001) and maintained at 53±12 degrees (P=0.003). Pre-op OPA was 30±11 degrees changing to 23±6-degree post-op (P<0.001) and maintained at 26±6 degrees (P=0.005). OPA relapse was similar in patients who underwent postoperative orthodontics (P>0.05). Overall, curvilinear MDO results in significant cephalometric improvements in SNB, MPA, and OPA. These improvements seem to remain relatively stable at 4-year follow-up. Investigation of long-term results is needed to better understand the risk/benefit ratio.